【剑指offer】用两个栈实现队列

Stack<Integer> stack1 = new Stack<Integer>();
Stack<Integer> stack2 = new Stack<Integer>();

public void (int node) {
    stack1.push(node);
}

public int pop() {
    if (stack2.isEmpty()){
        while (!stack1.isEmpty())
            stack2.push(stack1.pop());
    }

    return stack2.pop();
}